An ordinary electric steering lock device has a lock bar which is driven by a cam coupled to a motor. The lock bar is movable between a lock position where it is engaged with the steering shaft of a vehicle and an unlock position where it is not engaged with the steering shaft. When the lock bar is engaged with the steering shaft, the steering shaft is locked so that the steering shaft is not operable. When the lock bar is not engaged with the steering shaft, the steering shaft is unlocked so that the steering shaft is operable.
When the motor is kept running while the lock bar is at the lock position or at the unlock position, the motor may be overloaded. In this respect, an electric steering lock device equipped with a clutch mechanism has been proposed. The clutch mechanism is provided in the power transmission path between the motor and the cam to selectively block power transmission between the motor and the cam.
To quickly and surely lock and unlock the steering shaft, it is desirable to increase the drive force of the motor. However, the conventional clutch mechanism is so constructed as to be likely to be disengaged even with a relatively small load. Therefore, the drive force of the motor cannot be made so large.